You'll have to remove the door panel. There are screws around the perimeter, behind the door handle (a little round clip) and in the elbow rest (pop out that plastic insert)
There's a plastic inner cover, but I don't think you have to remove it. The speakers themselves are held in right there. Just unscrew and there you go. There's a plug in the back/side holding them on you'll need to carefully undo.
Size, I'm not 100% sure on that.
